The invention relates to magnetic thin film media and methods for their fabrication and more particularly to magnetic thin film disks having a pre-seed layer and a seed layer prior to an underlayer.
A typical prior art head and disk system 10 is illustrated in FIG. 1. In operation the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16. The magnetic transducer 20, usually called a xe2x80x9cheadxe2x80x9d or xe2x80x9cslider,xe2x80x9d is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and write heads 12, 23 travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13. The magnetic transducer 20 is positioned over points at varying radial distances from the center of the disk 16 to read and write circular tracks (not shown). The disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16. The disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited. The thin films 21 include ferromagnetic material in which the write head 23 records the magnetic transitions in which information is encoded.
The conventional disk 16 consists substrate 26 of AlMg with an electroless coating of NiP which has been highly polished. The thin films 21 on the disk 16 typically include a chromium or chromium alloy underlayer which is deposited on the substrate 26. The ferromagnetic layer in the thin films is based on various alloys of cobalt, nickel and iron. For example, a commonly used alloy is CoPtCr. Additional elements such as tantalum and boron are often used in the magnetic alloy. A protective overcoat layer is used to improve wearability and corrosion. The three film disk described above does not exhaust the possibilities. Various seed layers, multiple underlayers and laminated magnetic films have all been described in the prior art.
In particular, seed layers have been suggested for use with nonmetallic substrate materials such as glass. Typically the seed layer is a relatively thin layer which is the initial film deposited on the substrate and is followed by the underlayer. Materials proposed for use as seed layers include chromium, titanium, tantalum, Ni3P, MgO, carbon, tungsten, AlN, FeAl and NiAl. In U.S. Pat. No. 5,789,056 to Bian, et al., the use of a CrTi seed layer is described. The underlayers mentioned are Cr, CrV and CrTi.
The applicants disclose a thin film magnetic media structure with a pre-seed layer of CrTi. The CrTi pre-seed layer presents an amorphous or nanocrystalline structure. The preferred seed layer is RuAl. The use of the CrTi/RuAl bilayer structure provides superior adhesion to the substrate and resistance to scratching, as well as, excellent coercivity and signal-to-noise ratio (SNR) and reduced cost over the prior art.